1. Field of the Invention
The present invention relates to a positive photosensitive composition used in a manufacturing process of semiconductors, such as IC, manufacture of circuit substrates for liquid crystals, thermal heads and the like, and other photo-fabrication processes, a positive photosensitive composition for use in the positive photosensitive composition, a polymer compound used in the positive photosensitive composition, a manufacturing method of the polymer compound, a compound for use in the manufacture of the polymer compound, and a pattern-forming method using the positive photosensitive composition. More specifically, the invention relates to a positive photosensitive composition suitable for use in the case where far ultraviolet rays of 250 nm or less, preferably 220 nm or less, are used as exposure light sources, and electron beams are used as irradiation source, a polymer compound used in the positive photosensitive composition, a manufacturing method of the polymer compound, a compound for use in the manufacture of the polymer compound, and a pattern-forming method using the positive photosensitive composition.
2. Description of the Related Art
Chemical amplification photosensitive compositions are pattern-forming materials capable of generating an acid at an exposed part upon irradiation with actinic ray or radiation, e.g., far ultraviolet rays, changing the solubility in a developing solution of the irradiated part and non-irradiated part with actinic ray or radiation by the reaction with the acid as a catalyst, and forming a pattern on a substrate.
When a KrF excimer laser is used as the exposure light source, resins having poly(hydroxystyrene) as a fundamental skeleton low in absorption in the region of 248 nm are mainly used, so that a high sensitivity, high resolution and good pattern is formed as compared with conventionally used naphthoquinonediazide/novolak resins.
On the other hand, when a light source of further shorter wavelength, e.g., an ArF excimer laser (193 nm), is used as the exposure light source, even the above chemically amplified photosensitive compositions are not sufficient, since compounds containing an aromatic group substantially show large absorption in the region of 193 nm.
To cope with this problem, resists that contain a resin having an alicyclic hydrocarbon structure have been developed for an ArF excimer laser. For example, compositions containing resins having a polycyclic acid-decomposable repeating unit and a non-acid-decomposable repeating unit are disclosed in JP-A-2003-167347 and JP-A-2003-223001. These resins are chemically amplified resists having protective groups that are dissociated by the action of an acid and unstable to an acid, but now under the circumstances of further fining of the resist pattern is required, it is more and more difficult to obtain sufficient resist performance with these protective groups alone.
Therefore, for example, as disclosed in JP-A-2001-98034, JP-A-2000-214587 and JP-A-2001-106737, resist polymers in which a crosslinking site that is dissociated by the action of an acid is introduced to the side chain of the resin containing a repeating unit having an acid-dissociating protective group are also examined.
This is by the mechanism that the crosslinkage is broken by the action of the acid catalyst and dissolution contrast between the exposed area and the unexposed area is improved. However, since a bifunctional monomer such as diacrylate is used in the polymerization of the polymer and crosslinking reaction occurs on the side chain of the polymer chain, the molecular weight distribution of the polymer formed is very great and solubility is low. In addition, a polymer of super high molecular weight is liable to be formed, so that a high molecular weight hardly soluble component difficult to be dissolved in an alkali developing solution is present even after being decomposed by acid, and development defect occurs due to the polymer component remaining undissolved at the time of fine pattern formation.
Also, as disclosed in JP-A-2001-98034, in the case where a crosslinked polymer having a crosslinking site having an acetal skeleton unstable to acid on the side chain of the polymer is used as a resist polymer, the polymer is very sensitive to acid, so that the preservation stability is inferior.
On the other hand, positive photosensitive resins having introduced an acid-dissociating structure into the main chain of a polymer are proposed in JP-A-2006-91762 and WO 2005/085301A1. These are the propositions to solve the problem of the above side chain crosslinking type polymers, but the effect is not sufficient.